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Hard to tell without knowing what year, make, and model of vehicle we are working on here. A speed sensor would not cause this, but bad engine or trans mounts could, or possibly a sticking valve body in the transmission.

The knock sensor is used to detect engine vibrations caused by preignition or detonation and provides information to the ECM, which then retards the timing to eliminate detonation.Here's a link on how to test and replace.Here's the sensor.

check the level of the transmission fluid while the engine is running.also has the transmission been "flushed"? a lot of shops just use dextron atf with the additives supplied by the supplier of the flushing machine.this can cause problems in toyotas.replacing the fluid with the correct (T IV) transmission fluidmay help.but if you are having this much trouble it may be too late.

1. Extremely harsh shifts from P or N, normal shifts at WOT: EPC (Electronic Pressure Control) solenoid failed. Easy fix in pan. Fix as soon as possible or hard parts will eventually break.2. Shift suddenly become very hard. When going from park to either reverse or drive it slams into gear. 1-2 and 2-3 shifts are also harsh. All gears seems to work. Problem may be intermittent: Check TPS for smooth electrical response. If the response is jumpy or erratic at all, replace TPS.There are two thing that may be happening that you have described, but you can tell which one it will be since your driving the Blazer. Both are simple to repaire, but to change the EPC. Your going to have to drop the transmission pan so that's going to be a transmission shop and call around, the EPC can be replace the same time there draining the transmission fluid when servicing the transmission which is about $110.00 for fluid and filter replacement and additional $65.00-$80.00 for the EPC valve. EPC (electronic pressure control) valveTPS (Throttle position sensor)Thank you for using Fixya and good luck. If it's the EPC failure, replace as soon as possible. may casue the sunshell to fractured or splines to sheared off.

sounds as if you may be looking in the wrong spot. If different gearing is drastically changing the symptoms you may want to check the trans. or torque converter. sudden pop with engine rpm increase and lack of power sounds like possible band breakage in transmission or impellor breakage in torque converter.